Research

Stephen F. Heinemann, a professor in the Molecular Neurobiology Laboratory, studies the molecular details of communication among brain cells. The synapse plays a key role in communicating information between brain cells and it is likely that biochemical changes at the synapse underlie some aspects of higher brain function. Most plausible theories of learning and memory depend upon changes in the efficiency of chemical synapses, which probably involves changes in receptors, ion channels and neurotransmitter release. It is also now known that these molecules can be directly involved in human disease. Most drugs that are used to treat mental illness are known to work either on the receptors or the metabolism of the transmitters at the synapse. The work in the laboratory is focused on the molecular biology and physiology of the glutamate and nicotinic receptors expressed in the brain. A major goal is to understand the regulation of synaptic function and the molecular biology of learning.

Among other notable achievements, his lab has isolated a gene containing the blueprints for a receptor critical to learning and memory, and identified the receptors that respond to nicotine. Since neurological ailments, such as Alzheimer's and Parkinson's; drug addiction; and mental disorders, such as depression and schizophrenia, are fundamentally disorders of brain cell communication, this research will provide new insights into the treatment of these disorders. Discoveries in Heinemann's lab are currently being used by pharmaceutical and biotechnology companies to develop drugs for stroke, epilepsy, Parkinson's and Alzheimer's diseases, as well as mental conditions, such as nicotine addiction, depression and schizophrenia.

"The work in our laboratory is focused on the
molecular mechanism by which nerve cells
communicate with each other at specialized
connections, or synapses. Recent work
in the laboratory has supported the idea
that many diseases of the brain result from
deficits in communication between nerve
cells or synapses."

For close to a decade, pharmaceutical researchers
have been pursuing compounds to
activate a key nicotine receptor that plays a
role in cognitive processes. Triggering it, they
hope, might prevent or even reverse the
devastation wrought by Alzheimer's disease.
Researchers in Heinemann's lab, however,
whose group first identified the brain receptors
that respond to nicotine, have discovered
that when the receptor, alpha-7, encounters
beta amyloid, the toxic protein found in the
disease's hallmark plaques, the two may
actually go rogue. In combination, alpha-7
and beta amyloid appear to exacerbate
Alzheimer's symptoms, while eliminating
alpha-7 seems to nullify beta amyloid's
harmful effects.

Alpha-7 is expressed all over the brain, in all
mammals, which means that it is probably
essential, but investigators have not yet discovered
for what. Intrigued by earlier studies
showing that beta amyloid seemed particularly
drawn to the alpha-7 nicotinic receptors,
Heinemann and his team hypothesized that
the receptors mediate beta amyloid effects
in Alzheimer's disease. To test their theory,
they crossed mice engineered to lack the
gene for alpha-7 with a mouse model for
Alzheimer's disease, which had been genetically
engineered to overexpress amyloid precursor
protein (APP), an antecedent to beta
amyloid. They then put the offspring through
a series of memory tests. Surprisingly, those
with both mutations—too much APP and
no gene for alpha-7—performed as well as
normal mice. The Alzheimer's mice, however,
which had the alpha-7 gene and also
overexpressed APP, did poorly on the tests.
Pathology studies revealed the presence of
comparable amounts of plaque in the brains
of both types of mice, but in those lacking
the alpha-7 gene, they appeared to have no
effect. Similar disparities were evident in
measurements of the synaptic function underlying
learning and memory.

These findings, which suggest a completely
different target for potential Alzheimer's
drugs than those that have been tried, could
have important implications for researchers
seeking to combat the disease.